In recent years, there has been an increase in research and development regarding ITS (Intelligent Transport Systems) which transmit/receive information between an infrastructure system and a vehicle or a mobile object (mobile terminal), in order to solve road transportation problems such as traffic accidents, traffic jams, etc. Examples of such system already put to practical use include: an automatic toll collection system which solve traffic jams around toll booths using an ETC (Electric Toll Collection) system; a road traffic information providing service which provide route guidance in cooperation with GPS (Global Positioning System) and a car navigation system in order to solve traffic jams; and a bus location system which enable the current location of a bus to be checked using a mobile terminal and provide notice of the waiting time required at a bus stop.
As described above, such systems have been put to practical use mainly for the purpose of solving traffic jams and displaying route information. In the future, there will be a demand for developing a driving support system which enables the vehicle side to receive and use information transmitted from the infrastructure system in order to prevent traffic accidents.
In this regard, a structure has been devised in which RFID tags which record identification information are embedded in the road surface, and a vehicle reads out and uses the information stored in the RFID tags to prevent traffic accidents. For example, there is a technique in which RFID tags store traffic information such as road work information, road signs, etc., and a vehicle reads out the traffic information thus stored in the RFID tags and displays the traffic information thus read out on a display unit (e.g., Japanese Laid-open Patent Publication No. 2006-31072). Furthermore, there is a technique which enables a vehicle to generate map information in the course of driving along an actual route by reading out identification information stored in RFID tags (e.g., Japanese Laid-open Patent Publication No. 2006-47291).
Moreover, a technique has been proposed in which, in an ad-hoc wireless network which provides wireless communication using multiple terminal apparatuses as relays, identification information stored in RFID tags is used to select effective relay terminal apparatuses (e.g., Japanese Laid-open Patent Publication No. 2006-295325).
FIG. 1 is a diagram which illustrates an example of a driving support system which prevents traffic accidents in the vicinity of an intersection.
The driving support system illustrated in FIG. 1 has a configuration including: four cameras 11, 12, 13, and 14, which acquire images of the intersection zone from different fields of view; four pedestrian sensors 21, 22, 23, and 24, which detect pedestrians crossing at crosswalks; a wireless infrastructure device 30 which acquires the images acquired by the cameras 11, 12, 13, and 14, and the detection results detected by the pedestrian sensors 21, 22, 23, and 24, which multiplexes the images and the detection results thus acquired, and which transmits the data thus multiplexed in multi-address transmission manner; and vehicles 40 which are running along traffic lanes.
FIG. 2 is a block diagram which illustrates the driving support system illustrated in FIG. 1. FIG. 3 is a diagram which illustrates an example of images displayed on a display device mounted on a vehicle.
It should be noted that FIG. 2 illustrates only the components of the wireless infrastructure device 30 and the vehicle 40, which are related to the driving support system. As illustrated in FIG. 2, the wireless infrastructure device 30 includes: a multiplexing unit 31 which acquires four images acquired by the four cameras 11, 12, 13, and 14, and detection results detected by the pedestrian sensors 21, 22, 23, and 24, and multiplexes the acquired images and the detection results so as to generate transmission data; and a transmission unit 32 which transmits, in a multi-address transmission manner using an antenna 33, the transmission data thus generated by the multiplexing unit 31. The vehicle 40 mounts: a vehicle installation wireless device 41 which receives the transmission data using an antenna 43; and a display device 42 which displays images based upon the data received by the vehicle installation wireless device 41.
The transmission data obtained by the wireless infrastructure device 30 by multiplexing the four acquired images acquired by the four cameras 11, 12, 13, and 14 and the four detection results detected by the four pedestrian sensors 21, 22, 23, and 24, is transmitted in a multi-address transmission manner. In each vehicle, upon receiving the transmission data, the four acquired images and the four detection results are acquired based upon the received data, and the acquired images and the detection results thus acquired are itemized and displayed on the display device 42 as illustrated in FIG. 3.
In the example illustrated in FIG. 1, for the driver of the vehicle 40A, which is just about to turn right, the vehicle 40C is in a blind spot because it is hidden by being on the far side of the large-size vehicle 40B on the near side. Accordingly, in some cases, the vehicle 40A could turn right without noticing the vehicle 40C going straight ahead, leading to a risk of collision with the vehicle 40C. With such a driving support system, as illustrated in FIG. 3, the images acquired by the camera 11, 12, 13, and 14 are displayed on the display device 42 mounted on the vehicle 40A. This allows the driver of the vehicle 40A to notice the vehicle 40C, thereby preventing such an accident.
However, with such a structure displaying the four images acquired by the four cameras 11, 12, 13, and 14, as described above, it is difficult for the driver to understand which acquired image corresponds to which particular traffic lane.